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Abstract:

The invention relates to a pelletizing press for producing pellets,
preferably from biomass, for use as fuel in fireplaces, comprising at
least one die having a plurality of bores for pressing the biomass, at
least one roll rolling on a rolling surface of the die, and at least one
drive device for the die and/or the roll. The aim of the invention is to
create a pelletizing press, which makes it possible to use a die having
as low a height as possible, and thus as short a bore length as possible.
The invention is characterized in that, for mounting the die, a carrier
plate seated in a substantially planar manner against the die is arranged
downstream of the die in the passage direction of the biomass. At least
one opening for releasing the bores of the die is arranged in the carrier
plate.

Claims:

1. A pelletizing press for producing pellets, preferably from biomass for
use as fuel in fireplaces, the biomass comprising fibers, chips, or
shreds containing cellulose and/or lignocellulose, and at least one
matrix having a plurality of boreholes for the compression of the
biomass, at least one roller adapted to roll on a rolling surface of the
matrix, and at least one drive device for the matrix and/or the roller
being arranged in the pelletizing press, wherein, to mount the matrix in
a feedthrough direction of the biomass, a carrier plate which presses
essentially flatly against the matrix is arranged after the matrix, and
at least one opening for exposing the boreholes of the matrix is arranged
in the carrier plate.

2. The pelletizing press according to claim 1, wherein a substantially
larger passage is arranged in the carrier plate for at least each
borehole.

3. The pelletizing press according to claim 1, wherein at least two
matrix segments are arranged on the carrier plate as the matrix and/or
the carrier plate comprises multiple carrier plates.

4. The pelletizing press according to claim 3, wherein at least one
intermediate layer is arranged between the carrier plate and the matrix
or all matrix segments.

5. The pelletizing press according to claim 1, wherein the carrier plate
has substantially larger external dimensions than the matrix.

6. The pelletizing press according to claim 1, wherein at least one guide
means is arranged between the carrier plate and the matrix for the
fixation of the location and/or the play of the matrix to the carrier
plate.

7. The pelletizing press according to claim 6, wherein at least one
clamping sleeve and/or one side wall is arranged on at least one part of
an edge of the matrix as the guide means.

8. The pelletizing press according to claim 1, wherein the matrix
consists essentially of a first material and the carrier plate consists
essentially of a second material, the carrier plate material having lower
quality and/or lesser hardness and/or greater thickness than the matrix.

9. The pelletizing press according to claim 1, wherein at least two
boreholes of the matrix are combined in one passage of the carrier plate.

10. The pelletizing press according to claim 1, wherein the matrix is
implemented in parts or completely as hardened and/or made of a hardened
material and/or made of a carbonaceous steel.

11. The pelletizing press according to claim 1, wherein the carrier plate
is implemented having a sufficiently high stiffness that a deflection of
the matrix of not more than 0.025 mm on a section of 100 mm length occurs
during operation.

12. The pelletizing press according to claim 1, wherein a matrix having a
height of approximately 30 mm to approximately 60 mm, preferably 35 to 45
mm is arranged.

13. The pelletizing press according to claim 1, wherein a carrier plate
having a height of approximately 100 mm to approximately 200 mm,
preferably 125 to 175 mm is arranged.

14. The pelletizing press according to claim 1, wherein, in the case of a
ring matrix having externally or internally revolving rollers, the
carrier plate is implemented as a carrier ring and the carrier ring is
arranged on the outside or inside depending on the an application of the
matrix.

Description:

[0001] The invention relates to a pelletizing press for producing pellets
according to the preamble of claim 1.

[0002] The production of pellets, also referred to as granules, from fine
material or compacted and/or molten material is already known. The
production of pellets, or wood pellets from preferably chopped biomass,
such as wood chips, sawdust, or the like, is also already sufficiently
known and is propagated in the field of renewable energy sources as a
pioneering technology for climate protection, in particular in Europe.
Typically, chip material from the wood-processing industry is used as the
raw material, however, freshly cut timber or types of wood which are not
usable in the wood-processing industry or waste materials can also be
used. Pollutant-free base material is preferably to be used for the
market for wood pellets for supplying small furnace facilities in
single-family or multifamily houses. Block power plants or special
high-temperature furnace facilities for generating heat and/or obtaining
electrical energy (combination power plants) can also cleanly combust
pollutant-charged material (pellets made of particle board or
medium-density fiberboard with or without a coating or lacquering) in
small amounts, however.

[0003] The wood pellets are typically produced in so-called pelletizing
presses, in which the material to be compressed is pressed through
boreholes of a matrix by moving and/or actively rolling rollers, also
referred to as pan grinder rollers. The material (biomass) is shaped by
the boreholes and discharged as strands from the boreholes. Boreholes are
understood as all openings which are preferably implemented as
essentially cylindrical, and are arranged in a matrix to feed through and
shape the material. The boreholes can also have larger intake areas
(depressions) to improve the compression procedure and can be hardened or
can have hardened sleeves in the boreholes. A differentiation is made
between flat and ring matrices in the field of matrices. Rollers revolve
externally or internally around on ring matrices for the compression, on
flat matrices, the pan grinder rollers roll circularly (mill
construction) or linearly reversing. The invention is preferably
concerned with flat matrices of the latter construction, but can
optionally also be used with ring matrices. The possibilities for
preparing and scattering the biomass, or the post-processing (chopping of
the strands, cooling, storage, transport) of the pellets do not have to
be discussed in greater detail. Reference is made in this regard to the
prior art.

[0004] Due to the warming of the climate, which has been acknowledged
worldwide in the meantime, the industry has been forced to accelerate and
cheapen the large-scale industrial production of wood pellets. An
essential wearing part of the pelletizing presses is the matrix itself.
Due to the pressing and compaction of the biomass on the walls of the
boreholes, high coefficients of friction and pressures occur, which erode
the matrix boreholes and enlarge them over time. Simultaneously, it can
happen during the supply of the biomass that high-density elements, such
as rocks, pieces of metal, or the like, reach the flat matrix and are
pressed by the rolling rollers into the matrix. Distortions of the
surface of the matrix or frayed areas of the boreholes arise, this in
turn results in irregular compression of the residual layer of the
biomass on the rolling surface of the matrix, because the biomass of the
residual layer can no longer freely flow in all directions due to the
disturbances of the rolling surface. A corrugated residual layer arises,
which can result in incalculable machine-dynamic oscillations in the
pelletizing press. However, high-density clots of the biomass also form,
which in turn further damage the rolling surface of the matrix and/or
cause increased wear during the passage through the boreholes. In the
extreme case, faulty rolling surfaces result in "knocking" or also
"banging" rollers, which are harmful overall for the pelletizing press,
but also in particular for the rollers and the matrices.

[0005] However, it cannot be prevented in the nature of the production
that damage or wear of the matrix occurs over a certain period of
production time. The reconditioning of a matrix per se can be performed
by many types of reconditioning possibilities, such as grinding/planing
off the entire matrix, deposit welding in the case of depressions, or
drilling out local damage or a borehole and inserting a closure or a
sleeve. Matrices having wear-resistant coatings or surface hardening are
sufficiently known.

[0006] In the design of a matrix for a pelletizing press, up to this
point, passage boreholes have been introduced into a solid material. The
solid material is designed in vertical extension, which essentially
corresponds to the alignment of the passage boreholes, in such a manner
that it can bear the required forces of one or more pan grinder rollers
during the pelletizing procedure. This typically results in a matrix type
of more than 100 mm, depending on the starting product to be compacted.
In order to keep the wear within limits, hardening the matrix and/or
inserting sleeves into the boreholes, which have a higher quality
material and/or are replaceable (DE 27 08 562 A1), is known.

[0007] However, these solutions in turn require a high investment in order
to prepare the required deep-hole boreholes in the matrix. In addition,
there is the required work in order to adjust the boreholes on the intake
side to the material to be compressed (e.g., expansion in conical shape)
or deposit or through-hardening measures. The mentioned introduction of
the wear sleeves is also time-consuming and requires very precise fits.
It has therefore been shown that the matrix has become one of the most
expensive machine elements of a pelletizing press in the meantime (due to
the increased raw material and man-hour prices).

[0008] The object of the invention is to provide a pelletizing press of
the above-mentioned type for producing pellets, which also allows a
matrix to be used, which has the least possible height and therefore the
shortest possible length of the boreholes.

[0009] The achievement of the object for a pelletizing press is that, to
mount the matrix in the feedthrough direction of the biomass, a carrier
plate pressing essentially flatly against the matrix is arranged after
the matrix and at least one breach for exposing the boreholes of the
matrix is arranged in the carrier plate.

[0010] A matrix made of high-quality material can advantageously now be
implemented cost-effectively having the lowest possible thickness. In
particular, bending-resistant mounting of the matrix is thus possible.
The biomass is to be sufficiently compressed inside the matrix and is to
have the required strength and consistency after exiting from the
boreholes. It is ensured by the planar carrier plate that the sag of the
matrix remains in a controllable scope and has no consequence on
operation during the pelletizing. The matrix can therefore preferably be
manufactured from a high-strength, in particular low-wear and/or very
expensive material, since it is implementable and usable very "thin" or
with the least possible material expenditure. Hardened materials are also
conceivable, in particular the use of through hardened purchased parts,
which are inexpensive to purchase and only still have to be drilled.
Matrices which tend to become brittle or tend to fracture from
oscillation or continuous use can be supported using an intermediate
layer to the carrier plate, which results in outstanding damping in
relation to harmful oscillations. A plastic plate is preferably used for
this purpose, which simultaneously reduces or even prevents possible
manufacturing inaccuracies or support problems on the carrier plate. With
the teaching of the invention, one is capable of implementing the matrix
itself as a wearing element, which is easier to manufacture, easier to
handle, and more cost-effectively replaceable because of its smaller size
and accompanying minimization of weight. This is true in particular in
the case of a multipart matrix, which can be readily implemented because
of the carrier plate arranged in the pelletizing press. It is
comprehensible that the carrier plate is again in turn supported in the
pelletizing press. If the carrier plate is arranged as a ring plate, the
carrier plate accepts the compression forces applied by the pan grinder
rollers and distributes them according to the typical practice in the
respective pelletizing press arrangement. The carrier plate in
conjunction with a suitable matrix is also distinguished in this point in
particular by the refining possibility for replacing existing matrices
and mounting them in pelletizing presses. Therefore, it may be possible
in the scope of the invention to retrofit existing pelletizing presses
and to subsequently mount a matrix with a corresponding carrier plate.

[0011] In an expansion of the object in the case of a multipart matrix in
a pelletizing press, the rolling of the roller can be improved at the
joint edges of the matrix segments and/or the pelletizing press is to be
made capable of using matrix segments of different heights with uniform
quality of the rolling surface.

[0012] In particular, the present invention allows the matrix itself to be
manufactured as thin as possible, for example, 30 to 100 mm tall,
preferably 40 to 80 mm tall, and above all to be used without deflection.
Since it can be sufficiently supported by the carrier plate, a very
costly material or a through-hardened steel or a very hard steel or
stainless steel can also be used for this purpose. Costly chromium steels
or martensitic steels therefore no longer represent a reason for
obstructing investment because of the decreased costs because of the
decreased material use.

[0013] It is obvious that strands exit from the boreholes of the matrix,
which break apart into pellets, which have a greater or lesser length,
depending on the biomass used or a pelletizing press having a scissors
device for dividing the strands, which is not shown but is possible.
However, it has been shown that a cutting device is not necessary after
the carrier plate in most cases. Wood pellets in particular tear off
independently from the biomass strand exiting from the boreholes of the
matrix solely due to the vibration in the pelletizing press. In
combination with special processing applications such as temperature,
(natural) adhesive additive, or similar applications, however, it can
occur that the strands are implemented as relatively resistant to
breaking apart. In this regard, it can be advantageous to implement the
passages in such a manner that they are only expanded slightly in
relation to the boreholes or, with a grooved embodiment of the passages,
to implement the groove extension essentially parallel to the rolling
line of the roller and therefore to cut the biomass into
commercially-typical pellet sizes using a cutting blade which essentially
follows the same movement as the roller at regular intervals. According
to the understanding of the present invention, the carrier plate or its
passages does not form an extension of the boreholes of the matrix in
that it does not assume a supporting or shaping task in relation to the
biomass, nonetheless, depending on the embodiment variation, the passages
being able to be used as stops for a movable or rotating blade for
dividing the strands. Further advisable and possible embodiments are
described hereafter:

[0014] To support the matrix, the carrier plate can be arranged
essentially on the joint edges of the matrix segments and/or overlapping
the joint at the edges of the matrix. The latter is preferably advisable
in the case of narrow matrices. However, the joint edges of the matrix
segments are preferably particularly supported by the carrier plate, so
that sagging does not occur due to the heavy roller or even multiple
heavy rollers. In particular plastic sagging on a matrix results in
bulging of the joint edges and dropping or knocking rollers at the
transition from one matrix segment to the next. In a preferred exemplary
embodiment, an essential property of the passages of the carrier plate is
that they are introduced as large as possible, possibly even as grooves
or openings in the carrier plate, so that the static carrying capacity
for the matrix is essentially sufficient and it experiences no or only
harmless sagging. It is also advisable according to a further exemplary
embodiment to implement the passages as substantially larger than the
boreholes, the exiting strands, or the pellets. If mechanically cutting
apart the pellets appears advisable, independently of the size of the
passages, a cutting device can be arranged on the side of the carrier
plate facing away from the matrix. For expedient replacement and in
particular in the case of a plurality of matrix segments, it is
preferable for the individual matrix segments to be essentially identical
or similar. This preferably applies to the arrangement of the boreholes,
the geometry, and/or the joint edges to the adjacent matrix segments.

[0015] The joint edges of the matrix segments are particularly preferably
arranged essentially parallel to the rolling line of the roller. In a
further exemplary embodiment, the joint edge is particularly preferably
arranged essentially at an angle to the rolling line of the roller, the
angle being able to cover a range between 0 and 35°.

[0016] In particular, however, to join the matrix segments to one another,
it is preferable for the joint edges to be implemented as
tongue-and-groove connections and/or as zigzag connections and/or as
arrow-shaped connections. The above exemplary embodiments may be applied
particularly advantageously in a matrix which consists of matrix segments
which are arranged in a plane. The matrix would preferably be implemented
as rectangular or circular for this purpose. The matrix and/or the
carrier plate is particularly preferably implemented as partially or
completely hardened and/or made of hardened material. In different types
of embodiment of the carrier plate, it can consist of multiple carrier
segments. In this case, the joint edges of the carrier segments can
substantially differ from the joint edges of the matrix segments in their
location to one another and/or in their embodiment. This is used to
improve the support of the matrix, the special measures which were
proposed above for the rolling surface not having to be applied for the
joint edges of the carrier plate. Overall, the action of the carrier
plate is such that the sag of the matrix is less than 0.05 mm along the
rolling line of the roller, if the matrix has a width of 200 to 300 mm.

[0017] To avoid the transmission of vibrations and/or heat, an insulating
and/or damping intermediate layer can be arranged between the matrix or
the matrix segments and the carrier plate. This intermediate layer can be
supported by a further intermediate layer for the height compensation or
replaced with a correspondingly thicker intermediate layer. At least one
plastic, an insulation, a metal plate, and/or a hydraulic cushion would
be conceivable as the intermediate layer. The latter is preferably
adjustable in its action. At least one hydraulic and/or pneumatic
positioning device can be arranged between the matrix or the matrix
segments on the carrier plate. This positioning device can particularly
preferably be used to form a uniform rolling surface made of matrix
segments of different heights. At least one plastic, an insulation, a
metal plate, and/or a hydraulic cushion would be conceivable as the
intermediate layer. The latter is preferably adjustable in its action. If
an intermediate layer is used, the passages of the carrier plate are
preferably completely or partially reproduced therein. However, only the
number and the location of the boreholes can also be reproduced.

[0018] Correspondingly, in a further exemplary embodiment, a substantially
larger passage in the carrier plate is assigned to at least one borehole.
In addition to the matrix, the carrier plate can also consist of multiple
segments, which are assembled according to typical joining methods. The
carrier plate particularly preferably has substantially larger external
dimensions than the matrix. Furthermore, it is advisable if at least one
guide means for the fixation of the location and/or the play of the
matrix to the carrier plate is arranged between the carrier plate and the
matrix. Such a guide means can be at least one clamping sleeve and/or a
side wall on at least one part of the edge of the matrix. The matrix
particularly preferably essentially consists of a first material and the
carrier plate (9) consists of a second material, the carrier plate
consisting of a material of lower quality and/or lesser hardness and/or
greater thickness than the matrix.

[0019] In a further positive embodiment, at least two boreholes of the
matrix are combined in a breach of the carrier plate.

[0020] The matrix is preferably implemented in parts or completely as
hardened and/or from hardened material and/or from at least one
carbonaceous material. Of course, the matrix itself can also consist of
one or more assembled parts, according to the current prior art. It is
advantageous in particular if the carrier plate is implemented having
such a great stiffness that bending of the matrix of no more than 0.025
mm in a section of 100 mm length occurs during operation. For example, in
the case of a pan grinder roller rotating in a plane in a pelletizing
press, this would mean that the ring matrix essentially has a sag of 0.05
mm in a rolling line of 250 to 350 mm, more specifically preferably a sag
of 0.05 mm in 300 mm. The matrix is to be arranged having a height of
approximately 30 mm to approximately 60 mm, preferably 35 to 45 mm. In
contrast thereto, it is preferable that a carrier plate 9 has a height of
approximately 100 mm to approximately 200 mm, preferably 125 to 175 mm.
In addition to an application of the carrier plate in a flat matrix, of
course, an application of the carrier plate in a ring matrix is also
conceivable, the carrier plate being implemented as a carrier ring and
the carrier ring being arranged on the outside or inside depending on the
application of the ring matrix.

[0021] Further advantageous measures and designs of the object of the
invention are disclosed in the subclaims and the following description of
the drawing.

[0022] In the figures:

[0023] FIG. 1 shows a top view of a rectangular multipart flat matrix and
a carrier plate located underneath in a pelletizing press having a
reversing roller,

[0024] FIG. 2 shows a section along section line in FIG. 1 through the
multipart matrix and the carrier plate,

[0025] FIG. 3 shows a top view of a multipart circular matrix having a
multipart carrier plate arranged underneath in a pelletizing press having
a revolving roller,

[0026] FIG. 4 shows a section along a section line in FIG. 3 through the
multipart matrix and the multipart carrier plate,

[0027] FIG. 5 shows a simplified view of possible joint edges of the
matrix segments to improve the rolling of the roller,

[0028] FIG. 6 shows a section through a multipart matrix having matrix
segments of different heights,

[0029] FIG. 7 shows a simplified view of an actively movable and
adjustable positioning device for the matrix segments or a matrix in a
carrier plate, and

[0030] FIG. 8 shows an enlargement of a partial section according to FIG.
7 with illustration of a clamping sleeve.

[0031] FIG. 1 shows a top view of a rectangular multipart flat matrix 4,
which is laid on a carrier plate 9. A roller 5 rolls on the matrix 4
and/or the matrix 4 is moved together with the carrier plate 9 in a
reversing manner from left to right and back. In the drawing, a movement
to the right in the rolling direction 6 is shown in particular. The
matrix 4 consists according to the drawing of six matrix segments 7, 7',
. . . , 7'''' '', which are each arranged rotated by 180° and
pressing against one another at the joint edges 2. The angled arrangement
of the joint edges 2 having an angle 16 to the rolling line 14 of the
roller 5 allows soft rolling on the matrix 4. It is unimportant whether
the matrix 4 is moved, or whether the roller 5 is moved and/or the roller
5 also has an independent drive for independent rotation in addition to
the movement direction. Boreholes 13 are arranged in the matrix 4, which
preferably correspond to the passages 8 of the carrier plate 9. Of
course, it is possible that one large passage 8 corresponds to multiple
boreholes 13, as shown on the top left in FIG. 1 with the aid of a
grooved passage 8.

[0032] According to FIG. 2, the biomass 1 is scattered onto the matrix
during production (preferably in front of each roller 5) and pressed by
the rolling roller 5 into the boreholes 13 in the direction of the
feedthrough direction 12. A residual layer 11 can form on the rolling
surface 19 after the passage of the roller 5. After passing through the
boreholes 13, strands or pellets 10 form upon exit from the boreholes 13
on the flat side 20, which require further treatment or further
transport.

[0033] An alternative embodiment of the pelletizing press 3 is shown in
FIG. 3, which now uses revolving rollers 5 and a circular matrix 4 made
of multiple matrix segments 7 to 7'''''', which are arranged like slices
of a cake. The carrier plate also forms the foundation for a preferably
thin matrix 4 here, which consists of multiple matrix segments 7 to
7''''''. The simple capability for direct replacement of damaged matrix
parts and repair during operation also exists in the case of cake-shaped
matrix segments 7 to 7'''''' with the same embodiment. For this purpose,
at least one matrix segment 7 to 7'''''' is preferably kept in reserve in
the area of the pelletizing press 3 and replaced as needed after removing
a damaged matrix segment.

[0034] FIG. 4 again shows a sectional view, in a further embodiment, the
carrier plate 9, 9' being implemented in multiple parts, but having
passages 8 for feeding through the pellets 10 in the feedthrough
direction 12.

[0035] FIG. 5 shows multiple exemplary possibilities for connecting matrix
segments 7 to 7'''''' in such a manner that the rolling line 14 of the
roller 5 is not identical to the alignment of the joint edges 2. As is
obvious in the left of the figure, a joint edge 2 can be implemented as
an arrow edge for this purpose. The roller 5 having its rolling line 14
therefore does not roll suddenly over the joint edge 2, but rather over a
longer area. A zigzag connection between multiple matrix segments 7 to
7'''''' is shown on the right side. It is also obvious here that the
matrix segment 7', for example, can be readily lifted up and replaced
with a similar or identical matrix segment. In the event of unequal
heights of the matrix segments after long wear and polishing or grinding
procedures, an optimum rolling surface 19 is no longer ensured.

[0036] In order to nonetheless be able to use these matrix segments, it is
possible according to FIG. 6 that an intermediate layer 17 is inlaid
below a thinner matrix segment 7', which compensates for the height
difference to the adjacent matrix segments 7 and 7''. The intermediate
layer 17 therefore presses against the flat side 20. In an alternative
embodiment, the matrix 4 is embedded in a type of "planar groove" in the
carrier plate 9, so that the matrix 4 or the matrix segments 7, 7' . . .
obtain a fixation, which is required for operation, by means of the guide
means 21 thus resulting. The guide means 21 can also be implemented
differently, of course.

[0037] FIG. 7 shows an alternative embodiment in which positioning devices
18, which are introduced in the case of the matrix segment 7' having an
original height and are correspondingly extended in the case of a matrix
segment 7 of lesser height in order to implement a level rolling surface
19, are arranged in the carrier plate 9. To improve a uniform force
transmission between the positioning devices 18 and the matrix segments,
suitable intermediate layers can also be provided here as force
distributors. Through the positioning devices 18, it would be
quasi-possible to mount the matrix and/or the matrix segments on a
hydraulic cushion. An alternative to a guide means 21 for the fixation of
the location and/or the play of the matrix 4 to the carrier plate 9 is
once again arranged in FIG. 7. This can be at least one side wall, which
is installed upright or associated with the carrier plate 9, of the
carrier plate 9, each is optionally provided at regular intervals. The
guide means 21 is visible in section on the left in the drawing and
upright on the carrier plate 9 at the right rear as a top view having
reference sign 21'. The guide means 21 can be implemented in one piece
with the carrier plate 9 and can represent a protrusion or a bulge in
this case. Alternatively, an L-profile would be conceivable, which
overlaps the matrix 4 at least in the outside area.

[0038] The guide means 21 can also be implemented as a side wall for
delimiting the filling area or the rolling surface 19 of the biomass 1.
Two corresponding pocket hole boreholes 23 of the matrix 4 and the
carrier plate 9 are again shown in the right partial view.

[0039] FIG. 8 shows a sectional top view of an enlargement of this pocket
hole borehole 23 having an inserted clamping sleeve 22. A clamping sleeve
22 has the advantage in this context that thermal expansion of the matrix
or fitting inaccuracies can be readily absorbed, without the clamping
sleeve 22 shearing off, in contrast to a bolt. The clamping sleeve
consists of a type of tube, which has an opening in the axial direction.
Slight displacement advantageously also does not worsen the result of the
pelletizing, since minimal displacements or imprecise dimensional
accuracies can be compensated for without difficulty due to the passages
8, which are larger than the boreholes 13.

[0040] A further exemplary embodiment for optimizing the drilling pattern
on the rolling surface 19 in the case of extreme forces and/or a large
number of boreholes 13 is not shown in the figures. For this purpose, the
boreholes 13 in the area of a joint edge 2 of a matrix segment 7, 7', . .
. , to form a uniform drilling pattern on the rolling surface 19, are
arranged diagonally inside the matrix segment 7, 7' . . . in such a
manner that the carrier plate 9 is not tangent in the area of the joint
edge 2. In other words, this means that the boreholes 13, which extend
essentially from one flat side (rolling surface 19) to the other flat
side 20, are arranged diagonally from the rolling surface 19 in the
direction of the adjacent boreholes 13 at the edge of one matrix segment
with uniform drilling pattern. Therefore, the possible support area for
the carrier plate 9 on the bottom side of the matrix segments is
increased at the joint edges 2. The diagonally extending boreholes 13 are
not restricted to this area or this application, however.

[0041] Fundamentally, efforts have been made to produce a matrix,
preferably from a uniform steel. For example, a so-called knife steel
such as X46Cr13 (1.4034) is particularly suitable for this purpose,
which, having a martensitic microstructure and being stainless,
represents a good compromise between corrosion resistance, service life,
and susceptibility to brittle fracture. The pelletizing press 3 is
particularly preferably suitable for producing pellets 10 from biomass 1
for use in fireplaces, but can also be safely and expediently used in
other fields.